Method containing

packages/intl-segmenter/segmenter.ts:456–515

(positionInput: number)

  }

  containing(positionInput: number):
    | {
        segment: string
        index: number
        input: string
        isWordLike?: boolean
      }
    | undefined {
    if (typeof positionInput === 'bigint') {
      throw TypeError('Index must not be a BigInt')
    }

    let position = Number(positionInput)

    //https://tc39.es/ecma262/#sec-tointegerorinfinity
    // 2. If number is NaN, +0𝔽, or -0𝔽, return 0.
    if (isNaN(position) || !position) {
      position = 0
    }
    // 5. Let integer be floor(abs(ℝ(number))).
    // 6. If number < -0𝔽, set integer to -integer.
    position = Math.floor(Math.abs(position)) * (position < 0 ? -1 : 1)

    if (position < 0 || position >= this.input.length) {
      return undefined
    }

    //find previous break point
    let previousBreakPoint = 0
    if (position === 0) {
      previousBreakPoint = 0
    } else {
      const checkString = this.input
      for (let cursor = position; cursor >= 0; cursor--) {
        const {breaks} = this.segmenter.breaksAt(cursor, checkString)
        if (breaks) {
          previousBreakPoint = cursor
          break
        }
      }
    }
    let checkString = this.input.substring(previousBreakPoint)
    //find next break point
    for (let cursor = 1; cursor <= checkString.length; cursor++) {
      const {breaks, matchingRule} = this.segmenter.breaksAt(
        cursor,
        checkString
      )
      if (breaks) {
        const segment = checkString.substring(0, cursor)
        return createSegmentDataObject(
          this.segmenter,
          segment,
          previousBreakPoint,
          this.input,
          matchingRule
        )
      }